The exploration of macromolecular binding to immobilized ligands through the measurement of changes in surface plasmon resonance (SPR) measured in real-time has given new insight into how these processes occur. For example, the real-time binding of the full-length p51 ETS1 to its cognate DNA has been characterized as 'fast-on, fast off' binding while by contrast, the alternate splice product, p42 ETS1 is a 'slow-on, slow off' binder to the same cognate DNA sequence. Each of these proteins has complex, "change-of-state" binding kinetics. Such findings have justified studies of other DNA binding proteins in order to determine if SPR measurements could distinguish different kinetic mechanisms.